Method for completing oil wells



Oct. 22, 1940. 1. s SALNIKOV METHOD FOR COMPLETING OIL WELLS Filed July25, 1939 j INVENTOR.

BY I

/ ATTORNEY.

Patented Oct. 22, 1940 UNITED STATES METHOD FOR'COMPLETING OIL WELLSIvan S. Salnikov, Tulsa, Okla, assignor to Standard Oil DevelopmentCompany, a corporation of Delaware Application July 25, 1939, Serial No.286,312

\ 3 Claims.

The present invention is directed to a method for completing an oil welltraversing a plurality of producing horizons, and has for its particularobject the provision of a completion method 5 which makes possible theproduction of oil from the various horizons simultaneously, if desired.

In the past it has been customary, in the completion of oil wellsthrough a plurality of producing horizons, to set casing to the'lowestproduclng horizon which was ordinarily produced first.

In order to produce the higher horizons the casing was perforated bymeans of a gun perforator or other suitable means. This procedure hadthe drawback that the upper producing horizons. were not made availableto the operator for treatment for the improvement of production.Moreover, the perforations simply exposed a very small part of theavailable producing surface so that the rate of production was oftenmuch lower than the potential of the horizon.

According to the method of the present invention, a welltraversing aplurality oi producing horizons is completed by setting casing to thebottom producing horizon in the well and includ ing in the string ofcasing opposite the various producing horizons a section or numberofsections of drillable metal. The casing, including the drillablesections, is ordinarily set so as to permit production of the lowermosthorizon. If it is desired to produce from a plurality of horizons at onetime, the drillable sections opposite the upper horizons which it isdesired to produce, are drilled out at the time the cement plug isdrilled out to expose the lowermost horizon. If desired, however, thelowermost zone can be produced independently and then the higher zonescan be produced in sequence, if desired, by simply drilling out thecasing opposite them.

The present invention will be more clearly understood from the followingdetailed description of the accompanying drawing in which the singlefigure is a section through the well completed in accordance with thepresent invention.

Referring to the drawing in detail, numeral I designates a bore holetraversing a plurality of substrata including an oil bearing substratum2 and a second oil bearing substratum 3. Set in the bore hole in theusual manner is a string of casing l, the sections of which are made ofthe usual steels. Included in the string of easing opposite theproducing zone 2 is a section 5 of casing made of drillable material andhaving a reduced diameter. It will be understood that it is notnecessary to make this section of reduced diameter, but this representsthe best practice (ill. 166-21) under the present invention. Thematerial employed may be any of the known' readily drillable metals,such as aluminum alloys 01' various types. In addition to aluminumalloys may be mentioned magnesium alloys, resins, hard rubber, and the 5like. A typical aluminum alloy suitable for'this purpose is onecontaining 1% silicon, 1% Mg, 0.3% pr, the remainder being aluminum. Asuitable magnesium alloy is one containing 334.7% A1, 0.2% Mn, 0.3% Zn,0.5% Si, the remainder 10 being magnesium. One of the essentialproperties of this material is that it be of low specific gravity sothat the cuttings can be floated out with drilling mud of ordinaryweight.

In the drawing, the casing is shown just after 15 it has been cemented.It will be noted that the casing was set just above the producing sand3. The cement is designated by numeral 6, and the plug, which iscustomarily inserted in the casing to hold the cement in position untilit sets, is 20 indicated by numeral 1.

Ordinarily, in theeompletion of a well, after the cement is set, theplug 1 and the cement below it are drilled out and the hole is thenunderreamed opposite the producing sand 3. In the 25 practice of thepresent invention, when it is desired to produce from sands 2 and 3simultaneously, the section 5 01' the casing is drilled out on the downtrip to drill out the plug I. Then the underreamlng bit is put in andthe borehole 3o opposite sand 2 is first underreamed and then the borehole opposite sand 3 is underreamed. It will be understood that by thejudicious use of packers and plugs it is possible, according to thepresent invention, to subject the producing sands indivldually totreatments, such as acidizing, which are calculated to increase theirproductivity. It is also contemplated that producing sand 3 may beproduced until exhaustion and then the hole below section 5 is filledwith cement and section 5 o is drilled out, as hereinbefore described,for the production of oil from sand 2. sired, the drillable section ofcasing used'must have atleast as great an internal diameter, as; therest of the casing. of course, there may be J any number of producingsands.

The nature and objects 0f the present invention having been thusdescribed and illustrated, what is claimed as new and useful and isdesired to be secured by Letters Patent is:

1. In the completion of an oil well traversing a plurality of producinghorizons the steps which comprise setting casing of a selected diameterto a point adjacent the lowermost producing zone, including in saidcasing opposite each of the up- When this is de- V per producinghorizons a section of reduced didrilled-out sections to expose thesurface of the producing horizon.

2. A method according to the preceding claim in which the drillablematerial employed is an aluminum alloy.

5 3. A method according to claim 1 in which the drillable materialemployed is a magnesium alloy.

IVAN S. SALNIKOV.

